In the field of vehicle lighting units, a so-called projector type vehicle lighting unit utilizing a shade have been conventionally proposed. (See, for example, Japanese Utility Model Application Laid-Open No. Hei. 5-66807.)
FIG. 1 is a vertical cross-sectional view showing a vehicle lighting unit 200 described in Japanese Utility Model Application Laid-Open No. Hei. 5-66807.
As shown in FIG. 1, the vehicle lighting unit 200 includes: a projector lens 210 disposed on its optical axis AX extending in the front-to-rear direction of a vehicle body, the projector lens 210 having a rear-side focal point F; a light source 220 disposed behind the rear-side focal point F of the projector lens 210; a reflecting surface 230 configured to reflect light emitted from the light source 220 forward so that the light is directed toward the optical axis AX; and a shade 240 disposed between the projector lens 210 and the light source 220, the shade 240 configured to shield part of the light emitted from the light source 220 and reflected by the reflecting surface 230, the part of the light assumed to be directed upward and pass through the projector lens 210 if it is not shielded.
The light source 220 is a bulb light source such as a halogen bulb. The reflecting surface 230 can be a revolved ellipsoid having a first focal point F1 disposed at or near (i.e., substantially at) the light source 220 and a second focal point F2 disposed at or near (i.e., substantially at) the rear-side focal point F of the projector lens 210. The shade 240 can be disposed between the projector lens 210 and the light source 220 such that the upper edge 241 is positioned at or near (i.e., substantially at) the rear-side focal point F of the projector lens 210.
In this vehicle lighting unit 200 with the above configuration, the light emitted from the light source 220 can be reflected by the reflecting surface 220 and converged at or near (i.e., substantially at) the rear-side focal point F of the projector lens while part of the light can be shielded by the shade. Specifically, the light directed upward and assumed to be travel through the projector lens 210 can be shielded by the shade 240. Then, the light not shielded by the shade 240 can be projected through the projector lens 210 forward to form a low-beam light distribution pattern P on a virtual vertical screen assumed to be present in front of the vehicle body about 25 m away from the vehicle body. In this case the low-beam light distribution pattern P can include a cut-off line CL defined by the upper edge 241 of the shade 240.
As discussed above, the vehicle lighting unit 200 with the above configuration can shield the upward light assumed to pass through the projector lens 210 with the shade 240, thereby preventing the generation of glare to oncoming vehicles or preceding vehicles. However, the vehicle lighting unit 200 with the above configuration may not illuminate the left and right lateral areas AL and AR above the horizontal line H-H with light as shown in FIG. 2. This may be a problem in which pedestrians, hindrances, and the like assumed to be present in the left and right lateral areas AL and AR may not be illuminated with light.
FIG. 3 is a vertical cross-sectional view showing another projector type vehicle lighting unit (vehicle headlamp) utilizing a shade as disclosed in Japanese Patent No. 3798723.
As shown in FIG. 3, the vehicle headlamp 200 described in Japanese Patent No. 3798723 can have the same basic structure as, or a structure similar to, the conventional vehicle lighting unit 200 shown in FIG. 1.
The difference therebetween is that the shade 240 has a through hole 242 in the upper edge thereof.
As in the previous conventional vehicle lighting unit 200 described above, the vehicle headlamp 200 with the above-described configuration can form a basic light distribution pattern (being a low-beam light distribution pattern) Pa including a cut-off line CL defined by the upper edge 241 of the shade 240 as shown in FIG. 4.
In addition to this, this vehicle headlamp 200 can form an overhead light distribution pattern Pb above the horizontal line H-H at the center area to illuminate an overhead sign area with light. Specifically, the overhead light distribution pattern Pb can be formed by reflecting part of light emitted from the light source 220 by a part 231 of the reflecting surface 230 positioned below the optical axis AX, allowing the reflected light to pass through the through hole 242 formed in the upper part of the shade 240, and then allowing the passing light to pass through the projector lens 210 to be directed forward and obliquely upward. (See FIG. 4.)
Therefore, the vehicle headlight 200 with the above configuration can form both the basic light distribution pattern Pa and the overhead light distribution pattern Pb. In this case, the part 231 of the reflecting surface 230 is used for reflecting light for forming the overhead light distribution pattern Pb. This means that the area to reflect light for forming the basic light distribution pattern Pa is invaded in part.